Transistor design, particularly in the search for miniaturization, takes different criteria into account, particularly the required performance, and the technique of manufacture used.
The techniques for manufacturing the transistors shall preferably be accurate and inexpensive.
The performance of a field-effect planar transistor depends in particular on the geometry of the conduction channel connecting the drain and the source of the transistor. For example, the drain current, denoted ID, depends in particular on the ratio of channel width W to channel length L (W/L). One solution for obtaining a better drain current ID comprises for example reducing the length L of the channel in order to increase the electric field E between the drain and the source, without needing to apply too large a potential VDS between the drain and the source (E=VDS/L).
Furthermore, undesirable effects related to transistor geometry, such as edge effects, may appear and reduce transistor performance.
To meet these requirements, document U.S. 2005/0253134 proposes a “low gate” transistor with a cylindrical structure that gives a good W/L ratio and reduces the edge effects. To be more precise, according to one prior art alternative, the transistor is based on a fiber onto which is deposited a layer of semi-conductor, the fiber core being empty. The drain and source electrodes are implemented on the inner periphery of the layer of semi-conductor, symmetrically relative to the fiber axis. The assembly so constituted is surrounded by an insulating layer, and a layer forming the gate is then deposited over the entire outer periphery of said insulating layer.
Although the prior art solution is able to give a good W/L ratio by playing on the length of the transistor along the fiber, this solution demands complex and expensive manufacturing techniques.
In this context, the present invention proposes a field-effect transistor affording a different architecture from that proposed in the prior art, and that can be implemented with more straightforward and less expensive manufacturing techniques.